It is narrated from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: "None of you should let Bilal's (may Allah be pleased with him) call to prayer prevent him from his pre-dawn meal, for he gives the call to prayer so that the one who is offering voluntary prayers may return (to rest), and the one who is sleeping may wake up, and (the time of Fajr) does not become like this until (the light) becomes like this." The Imam (may Allah have mercy on him) says: Yusuf bin Musa also narrated this to us.